fs/9p: Fix invalid mount options/args

Without this fix, if any invalid mount options/args are passed while mouting
the 9p fs, no error (-EINVAL) is returned and default arg value is assigned.

This fix returns -EINVAL when an invalid arguement is found while parsing
mount options.

Signed-off-by: Prem Karat <[e-mail]>
Signed-off-by: Aneesh Kumar K.V <[e-mail]>
Signed-off-by: Eric Van Hensbergen <[e-mail]>

fs/9p/v9fs.c

···
 	{Opt_err, NULL}
 };
 
+/* Interpret mount options for cache mode */
+static int get_cache_mode(char *s)
+{
+	int version = -EINVAL;
+
+	if (!strcmp(s, "loose")) {
+		version = CACHE_LOOSE;
+		P9_DPRINTK(P9_DEBUG_9P, "Cache mode: loose\n");
+	} else if (!strcmp(s, "fscache")) {
+		version = CACHE_FSCACHE;
+		P9_DPRINTK(P9_DEBUG_9P, "Cache mode: fscache\n");
+	} else if (!strcmp(s, "none")) {
+		version = CACHE_NONE;
+		P9_DPRINTK(P9_DEBUG_9P, "Cache mode: none\n");
+	} else
+		printk(KERN_INFO "9p: Unknown Cache mode %s.\n", s);
+	return version;
+}
+
 /**
  * v9fs_parse_options - parse mount options into session structure
  * @v9ses: existing v9fs session information
···
 	/* setup defaults */
 	v9ses->afid = ~0;
 	v9ses->debug = 0;
-	v9ses->cache = 0;
+	v9ses->cache = CACHE_NONE;
 #ifdef CONFIG_9P_FSCACHE
 	v9ses->cachetag = NULL;
 #endif
···
 				  "problem allocating copy of cache arg\n");
 				goto free_and_return;
 			}
+			ret = get_cache_mode(s);
+			if (ret == -EINVAL) {
+				kfree(s);
+				goto free_and_return;
+			}
 
-			if (strcmp(s, "loose") == 0)
-				v9ses->cache = CACHE_LOOSE;
-			else if (strcmp(s, "fscache") == 0)
-				v9ses->cache = CACHE_FSCACHE;
-			else
-				v9ses->cache = CACHE_NONE;
+			v9ses->cache = ret;
 			kfree(s);
 			break;
 
···
 			} else {
 				v9ses->flags |= V9FS_ACCESS_SINGLE;
 				v9ses->uid = simple_strtoul(s, &e, 10);
-				if (*e != '\0')
-					v9ses->uid = ~0;
+				if (*e != '\0') {
+					ret = -EINVAL;
+					printk(KERN_INFO "9p: Unknown access "
+							"argument %s.\n", s);
+					kfree(s);
+					goto free_and_return;
+				}
 			}
+
 			kfree(s);
 			break;